1. Field of the Invention
The present invention relates to a honeycomb filter.
2. Background Art
A honeycomb filter has been proposed that has cell partitions arranged in the form of a honeycomb and a large number of cells sectioned by the cell partitions, wherein the ratio of the presence of open pores that are open in the surfaces of the cell partitions within the distance of 20 μm from the surfaces of the cell partitions in the depth direction is 7% or more (for example, refer to Patent Literature 1). It is stated that this filter can have a high resistance to separation of a loaded catalyst. Another honeycomb filter has been proposed that has partitions having porous partition bases and surface layers provided on the inflow sides of the partition bases, wherein conditions including the peak pore diameter of the surface layers, the porosity of the surface layers, the thickness of the surface layers, the mass of the surface layers per filtration area, and the average pore diameter of the partition bases are properly adjusted (for example, refer to Patent Literature 2). In this filter, a rapid increase in the pressure loss immediately after the initiation of trapping of particulate matter (PM) is not caused and the relationship between the amount of PM deposited and the pressure loss does not have hysteresis characteristics. Thus, the pressure loss in an initial state where PM is not deposited can be suppressed to a low value.